When data is transmitted at a high speed through a transmission line, such as a printed circuit wiring, inter-symbol interference (ISI) may occur due to the characteristics of the transmission line. Due to the ISI, an amplitude and a phase of a received signal may be distorted, and bit errors may occur in a signal at a receiver. Furthermore, as the length of the transmission line becomes longer and the transmission speed becomes faster, the amplitude and the phase of the received signal at the receiver may be significantly distorted.
In order to compensate for the distortion due to the ISI, the receiver can employ an adaptive decision feedback equalizer (DFE). The adaptive DFE compensates for a magnitude and a delay characteristic of the received signal in the receiver by updating a tap coefficient of the equalizer based on a channel characteristic. Additionally, in order to reduce the ISI of the signal at the receiver, the adaptive DFE can determine a pre-emphasis strength value based on the length of the transmission line and the data transmission speed, and pre-emphasizes a signal based on the determined pre-emphasis strength value to transmit the pre-emphasized signal.
In particular, a transmitter can pre-emphasize the data corresponding to a high frequency component to transmit the pre-emphasized data, since the high frequency component is more attenuated than a low frequency component when the high frequency component is transmitted through the transmission line. When the transmitter transmits data to the receiver, in order to compensate for the data signal, the data signal may be pre-emphasized based on an optimum pre-emphasis strength value.
A degree of attenuation of the high frequency component in the transmitted data signal is varied based on a length of the transmission line, such as a printed pattern formed on a printed circuit board (PCB). The optimum pre-emphasis strength value may be varied based on the transmission line length.
If the pre-emphasis strength value of the high frequency component of the transmitted data signal becomes excessively large, the size of a data eye pattern of the data signal received to the receiver may be decreased. A data communication system in which a transmitter and a receiver are used together has transmission conditions that can be variable, such as the transmission line length and the data transmission speed. Thus, some systems set a pre-emphasis strength value despite the variable transmission conditions.
It may be difficult to manually control the pre-emphasis strength value since the ISI increases when the data transmission speed becomes faster. When the conventional transmitter transmits a pre-emphasized data signal based on the pre-emphasis strength value that is manually set by a conventional pre-emphasis circuit in the conventional transmitter, the transmitter may not be able to verify whether the set pre-emphasis strength value is the optimum pre-emphasis strength value or not.